Cohn, who spent 26 years at Goldman Sachs, was the No. 2 executive at the firm after CEO Lloyd Blankfein. He will become director of the National Economic Council, an advisory role to Trump on US and global economic policy.

"Saying goodbye is hard," Cohn said on a company podcast recorded Monday morning. "You know, this has been 26 years, literally, I finish my 26th year next week — really hard. I always knew I would say goodbye — everyone has to leave someday — but it's hard."

He said he wanted to be remembered as a great partner — someone people could easily call, who people wanted to work with, and whose opinion was valued.

"You know, Goldman Sachs has a unique culture, and it's a culture that continues to evolve," Cohn said.

"I felt like I was part of the culture, and I was part of the evolution of the culture. I was here as a private company, I was here through the IPO, I've been here through the transition into a very public company."

In a statement on Monday, Cohn, who grew up in a working-class family in Ohio, said he shared Trump's vision of making sure every American worker had a secure place in a thriving economy.

Cohn will need to sell his shares in Goldman Sachs to avoid a conflict of interest, and he will be allowed to defer paying any capital-gains taxes from the sale. As of November 14, he held 872,712 shares, according to Bloomberg, currently worth about $207 million.

At Goldman, Cohn had advocated diversity within the firm. He was also known for his ability to build strong client relationships — in fact, he said, he typically saw more than 500 clients every year.

He said he would miss his clients and the people at the firm.

"Now I'm going onto a spectacularly new challenge, and I'm sure many of those voids will get filled," he said. "But this spot in my heart, in my mind, will be here for a long time."